1. Field of the Invention
This invention pertains to a device that provides for the selective adjustment and positioning of components relative to one another, particularly chair backs.
2. Description of The Prior Art and Objectives of the Invention
In the prior art, such as is specified in my U.S. Pat. No. 4,749,230, which is herein incorporated by reference, a device telescopes responsive to manual control and automatically, yet releasably locks in place responsive to the effect of gravity upon a locking pin. While such devices are reliable, economic and provide quick response, they do not provide substantial audible feedback to the user as to its current state. This has been found to be highly disconcerting to most chair occupants. In that regard, it has been found that users prefer a device that produces an audible "click" alerting the user that the device has engaged, or "locked" in a given position within its intended telescoping range. The problem is analogous to a "ON-OFF" button; most people expect and prefer a "click" indicating that a change in status has taken place. One object of the present invention is to provide such a mechanism with substantial audible feedback.
Another problem in devices that are gravity dependent is that they are not suitable for releasably locking two telescoping members, if not vertically oriented, where a great deal of movement is expected, or where, for example, the device is operated horizontally. A second object of the invention is therefore to address those situations. To that end, the improved device is provided with a spring, to forcibly propel the lock pin toward a position of engagement with a notch in the track member, producing a clearly audible "click", and insuring engagement of the lock pin in all sorts of orientations. The resulting combination, a gravity operated lock pin, along with a spring, provides a great degree of reliability in all sorts of situations, yet by virtue of its design, it is highly economical to manufacture.
One other problem encountered in the prior art is the need to make the telescoping members with a high degree of precision in order to obtain a snug fit that minimizes play between the members. Unfortunately, it is very difficult to economically make such an arrangement and obtain snug, yet smooth and responsive telescoping action; often situations arise where an interference fit has occurred, or else, a sloppy fit has been obtained resulting in a wobbly engagement. In the furniture industry, for example, all currently known devices of this type suffer from this problem. Therefore, one other object of the improved device is to provide for economically and reliably facilitating the smooth telescoping action of the elements and yet insure a snug fit, free of excessive play. Therefore, this object of the invention consists of providing several internal cavity faces on the track member with fixed and longitudinally disposed guide members, so that the support member telescopes in what is known in the art as a "running fit". These guide members are made of a resilient material such as nylon, and may be shaped like tubes. By judiciously selecting the wall thickness and durometer of the tubes, these guides can be made to automatically compensate for tolerance requirements between the track member and the support member. Alternatively, the support member may be grooved on its narrow sides so as to engage corresponding guide members in a "tongue-in-groove" or "keyed" like arrangement. The support member would therefore be able to telescope within the track member in a guided yet resilient fit across the longitudinal axis and across the transverse axis of the device simultaneously. In that manner, the track member can telescope snugly along the entire adjustment stroke of the device. If the support member happens to be manufactured slightly larger (or smaller) in width than optimally specified, the guide members will automatically deform to compensate. It should be realized that even a small departure from the optimal dimensions of any telescoping device, often only a few thousandths of an inch, can cause other elements attached to such a device to wobble unacceptably and breakage or binding may result. Wobbling of a chair back is very annoying and distracting to a chair occupant, so in this type of device, it is imperative to keep it to a minimum. In this embodiment of the improved device, the support member is kept from all manner of contact with the track member and is in contact only with the guide members. Therefore, the device is unlikely to bind, and will also be more tolerant to twists or deflections of the track member, which may occur during installation.
The device is extremely easy to operate. When used to adjust the height of a chair back relative to the chair seat, all the user needs to do is, while in the seated position, reach with the hands and lift the chair back to the next desired position. At that point, if the user lets go of the chair back, the device will automatically lock in that position and remain there until adjustment is again required. The device can be made to cycle from one uppermost position to one lowermost position by the biasing action of the cam slot in the support member and the locking action of the notches of the cam slot in the track member upon the locking pin.
These and other objectives and advantages will become readily apparent to those skilled in the art upon reference to the following detailed description and accompanying drawing figures.